Medical Textbook Understanding Development On the Beginning of Life

Scarr, S., Weinberg, R.A., and Levine A., Understanding Development, Harcourt Brace Jovanovich, Inc., 1986. page 86

“The development of a new human being begins when a male’s sperm pierces the cell membrane of a female’s ovum, or egg….The villi become the placenta, which will nourish the developing infant for the next eight and a half months.”